1. Field of the Invention
The present invention pertains to a protection device for use in the telecommunications field for protecting equipment connected to tip and ring conductor pairs. More particularly, the present invention relates to a thermal overload mechanism for providing a grounding path for tip and ring conductors during a power cross occurrence.
2. Description of the Related Art
Telecommunications systems typically employ protection mechanisms such as grounding devices located proximate a service subscriber location or central office to protect telecommunications lines from detrimental power surges and voltage spikes. The voltage spikes are usually caused by lightning striking telephone lines, and the power surges are caused by power crosses between telephone lines and high voltage power cables which occur, for example, as a result of high winds. In particular, grounding devices are used to provide a path to common ground for voltage surges caused by lightning strikes to prevent such surges from damaging equipment connected to tip and ring wires as well as to prevent injury to personnel working on the wires or on equipment.
In the event of a power cross situation, however, which results in the application of high currents and resulting high temperatures to protection mechanisms, a grounding path must also be formed to provide for the discharge of power surges which would, otherwise, adversely affect delicate telecommunications equipment and injure personnel. Known grounding protection mechanisms of the type employing solid state devices typically include a combination of a fuseable pellet or link in conjunction with a biasing spring. The fusable pellet will melt from the heat generated during a power cross occurrence, in which event the biasing spring will maintain connection of the tip/ring pair through a common ground. The drawback of this technique, however, is that the additional elements (such as the spring and fuseable link) must be added to the protection mechanisms during assembly, thereby increasing the cost and assembly time for such devices.